This invention relates to a yarn finish. More particularly, this invention relates to a spin finish for polyamide yarn to be processed into tire cord.
Various finishes for synthetic filaments are known. However, none of the prior art teaches the required combination of ingredients to achieve the specific beneficial results of the composition of this invention. The critical ingredients and amounts thereof are shown in the discussion below.
Many of the known finishes flash off of the yarn in high temperature processing. Others cause excessive loss of strength during cording operations. Still others fail to have emulsion stability or provide insufficient yarn lubrication. Representative prior art patents include U.S. Pat. No. 3,103,448 to Ross; U.S. Pat. No. 3,428,560 to Olsen; U.S. Pat. No. 3,560,382 to Finch; U.S. Pat. No. 3,575,856 to Anton; and U.S. Pat. No. 3,644,081 to Matsuda et al.
It has been suggested that an oxidized polyethylene wax mixed with mineral oil and a suitable emulsifier may be emulsified with water so as to minimize the quantity of lubricant required and provide an unusually even distribution of finish on the yarn. For example, our recent U.S. Pat. No. 3,917,893 discloses a spin finish for polyamide yarn comprising an oil in water emulsion, the oil portion consisting essentially of white mineral oil, an oxidized polyethylene wax, an ethoxylated phosphated oleyl alcohol and a sulfonated succinic acid ester of oleyl alcohol.
Although the spin finish disclosed in U.S. Pat. No. 3,917,893 is an important contribution to this art, its use on polyamide tire yarn has led to serious problems. More particularly, in production of tire cord from polyamide yarn bearing the spin finish of said patent, difficulty has been experienced in that the yarn suffers a significant loss of strength. Moreover, the finish tends to "smoke", i.e., give off fumes, when processed at the high temperature required for the cording operation. In production of tire cord, the tire yarn is conventionally twisted into three-ply cords and prepared for tire application by treatment with a standard resorcinol-formaldehyde-latex dip followed by heat treatment. The strength retained after this treatment is important to the quality of the resulting tires.